In the International Study of Kidney Disease in Children, 24 participating clinics in 12 countries throughout the world are conducting clinical surveys and therapeutic trials on major kidney diseases in children. Trials in progress include (1) the effect of cyclophosphamide patients with (a) focal segmental sclerosis and (b) anaphylactoid purpura; (2) the effect of prednisone in patients with membranoproliferative glomerulonephritis; (3) imuran in patients with severe lupus nephritis. Clinical surveys are being conducted on the natural history of patients with (1) the nephrotic syndrome; (2) recurrent hematuria; and (3) familial nephritis.